


Let the World Fall Away, I'll Be Here

by hyliank8



Series: Wartime Sanster AU Collection [1]
Category: Undertale (Video Game)
Genre: (sort of?), Angst, Blood, Character Death, Grief/Mourning, Guilt, Heavy Angst, Human-Monster War (Undertale), Loss, M/M, Magic Blood, Non-descriptive Fatal Injury, W. D. Gaster is not related to Skelebros, Wartime Sanster AU, soul bonds
Language: English
Status: Completed
Published: 2020-03-21
Updated: 2020-03-21
Packaged: 2021-02-28 19:47:09
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 1,056
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23242741
Author URL: https://archiveofourown.org/users/hyliank8/pseuds/hyliank8
Summary: Gaster promised Sans he would protect him.  Promised him that they would both survive this war, no matter the outcome—together....He shouldn't have made promises he couldn't keep.(Русский перевод доступен в заметках автора. || Russian translation is available in the author's notes.)
Relationships: W. D. Gaster/Sans
Series: Wartime Sanster AU Collection [1]
Series URL: https://archiveofourown.org/series/2146950
Comments: 17
Kudos: 43





	Let the World Fall Away, I'll Be Here

**Author's Note:**

> posting two fics in two days!!! this is a rarity for sure!!!
> 
> anyways hi!! i've had this wartime sanster au thing floating around in my head and i've written a lot for it but i've never posted any of itttt, so here's something!! of course the first thing i post for it is angst smh
> 
> Update: Translation into Русский/Russian [available here](https://ficbook.net/readfic/9698302) thanks to [Павлин](https://ficbook.net/authors/2914159) :)

The clashing of swords on the distant battlefield, the sound of magic attacks being discharged is all in the background now. All Gaster can focus on is his horribly wounded lover curled up in his arms, on the frail humming of his lover’s soul. Sans’ fragile breath is rattling in his chest; he seems to keep trying to say something, but his voice tapers off before he can force out a syllable. 

“Sans,” Gaster murmurs. “Don’t try to talk, okay, love? I’m here.”

Gaster feels hot tears prick at the corners of his eyes when he notices magic blood begin to seep once more through the bandage that he’d wrapped around Sans’ ribcage. Gaster had spent _hours_ dressing that wound, trying so hard to get it to stop bleeding, raking through his mind for every single detail about wound care that he’s ever learned.

But it wasn’t enough. _He_ wasn’t enough. He’s failed Sans, failed the love of his life and now Sans is… he's— 

“g-gast—” Sans finally manages to wheeze despite Gaster’s request, his fingers curling desperately into Gaster’s sleeve. “ ‘d-ding...s...”

“Hey, hey, it’s okay, my love,” Gaster coos, fighting with everything he has to keep his voice steady. “I’m right here, okay? I’ve got you, and I’m never leaving you, never. It’s going to be okay.”

Sans’ eyelights are hazy. His head twitches downward in what Gaster assumes is an attempt at a nod. Gaster can feel his lover’s soul shaking. He holds Sans close, never wanting to let go ever again.

“ ‘m scared,” Sans rasps, and Gaster’s soul wrenches in sympathy at his honesty, his vulnerability. He's always been one to hide his wounds, hide his pain from others, even when it's particularly detrimental to his health. But now… with his HP helplessly draining as the moments pass, he has nowhere to hide; he has nothing left. “i d-don’t… _hgk—!_ ”

Sans’ words are cut off with a gasp as his weak soul seizes up in pain, its feeble beating struggling to continue. Sans lets out a few fragile wheezes that turn into quiet, pained whimpers.

Gaster can _feel_ the unbearable pain coursing through his lover’s soul from their souls’ connection. It’s a mere echo of he knows what Sans must feel, but it’s painful even for Gaster. Gaster is sure that if Sans wasn’t so weak, he’d be screaming in pain.

Gaster holds his lover’s limp, shaking body close as his breathing slows. The humming of Sans’ soul is getting softer, weaker as the seconds pass, and with a horrible pit in his soul Gaster realizes that these are Sans’ final breaths. He’s so, so frail. How was it that mere days ago, he’d been perfectly fine? How was it possible for a single human to harm someone this badly?

“d-don’t,” Sans gasps, nearly incoherent. “i want it to s-s-s-....st…op.”

“I’m so sorry, my love,” Gaster’s soul clenches in pain with the sincerity of his own words. “If I could take it away, I would. I would do it in a heartbeat. But just… just focus on my voice, okay? Think about what I’m saying, focus on every word. ”

Sans doesn’t respond, looking too exhausted to do so. It seems that all he can do it stare at Gaster with his hazy eyelights, his expression nearly slack with just a hint of life in his clouded eyes. Gaster’s soul runs cold with fear as he realizes his lover’s consciousness is slipping away. _No, no…._

“H-hey, c’mon Sans, stay with me, okay?” Gaster says, a note of desperation in his voice. “C’mon, stay awake. You can do it, I know you can.”

Sans’ eye sockets begin to close, the light fading from his eyes. Gaster’s soul flutters with panic.

“N-no,” Gaster begs. “Sans, please! Please stay awake, _please_ stay with me, _please_ , I can’t—”

Sans’ eye sockets shut completely. Gaster extends his magic frantically, a CHECK running through his other half’s soul.

Sans’ soul is crumbling to pieces. Gaster wants to do something, _anything_ to help him, to keep him alive, but he knows it’s far too late. His injuries are far beyond the reach of even the most impressive healing magic. Sans’ body slowly relaxes, the intangible magic that acted as his muscles dwindling away. This is it; these are his final moments with the only person who has ever mattered to him.

He’d thought they’d die together, when they finally did go out. He imagined it would happen when they were old—after Gaster proposed to him, after they got married, after they moved in together and had long, fulfilling lives spent in each other’s company. He imagined them lying next to each other in a shared bed, cradling one another close and passing peacefully in the night.

But this is it. No final goodbye. No drifting off to sleep peacefully alongside one another. He is alive, and his lover’s broken, bloodied body is cradled to his chest.

And he’s covered in Sans’ blood, covered in his lover’s blood. It’s all over him, dripping from the wound in his lover’s chest onto his pants, soaking into the sleeves of his shirt; he lifts the hand that isn’t supporting Sans’ weight to examine it and it’s covered in red, Sans’ blood is on his hands and _you did this you killed him why weren’t you there why didn’t you save him you were supposed to protect him nononoNONONONONO—_

Sans’ soul shivers weakly, and Gaster lets out an anguished wail when he feels it finally shatter. His soul constricts in agony as the sharp pain of its splintering reaches him through the bond, and he can’t help the next tortured cry that escapes him when the bond between his soul and Sans’ is ripped away from him forever. A distant part of his mind is certain that this is the most painful thing he’s ever experienced.

Gaster can’t think, can barely breathe. Sans hasn’t turned to dust yet, but Gaster knows it’s only a matter of time. His mind is blank, unable to accept that Sans is gone, that the person he loves most in the world is gone. 

Gaster buries his head in the crook of his soulmate’s neck, desperate to breathe in his scent one last time.

All he can smell is blood.

“I can’t do this without you.”

**Author's Note:**

> whatever human did this to sans is fuckin toast LMAO
> 
> gaster’s lv probably gets to like 15 or something insane like that before he dies tbh
> 
> ALSO UH this is like. an au to an au, i guess. like when i think of what is “canon” to this au, this is not something tht actually happens. in fact i think i usually make this au mostly canon compliant? -ish. but, u kno, angst.
> 
> i talk about sanster a lot on [tumblr](https://hyliantimelordin221b.tumblr.com) and [ twitter (nsfw)! ](https://twitter.com/K8Maybe) come join me!!!
> 
> feel free to lemme know what u thought!!! ^^


End file.
